Re: New draft on Extra class LSP

["Adrian Farrel" <adrian@olddog.co.uk>]

Vishal,

Sorry, I'm a bit out of sync with this thread...

> I agree that priority could be used to setup LSPs that use the
> resources reserved (but not cross-connected) for recovery.
>
> However, the end-effect one wants to achieve is to have these
> LSPs be pre-empted by no other than working LSPs that legitimately
> need to use those resources when a fault affecting those working
> LSPs occurs.

I disagree!
Suppose I have three services Gold, Silver and Bronze.
Bronze is unprotected, low priority.
Silver is protected, medium priority, allows extra traffic on protection
path.
Gold is high priority, 1+1 protected.

One would accept that Silver or Gold LSPs can pre-empt a Bronze LSP.
Why would you not allow a Gold LSP to pre--empt the protection path of a
Silver LSP?

Clearly you would not allow a Silver LSP to pre-empt another Silver LSP
(although you might - as a short-term measure - allow a Silver LSP working
path to pre-empt a Silver LSP protection path, it being better to have two
services set up unprotected than only one service: but this would be a
network policy matter)

> As I said in that note, perhaps it is indeed possible, by
> an appropriate choice of priority allocations and rules, to achieve
> this effect, but it appears to me that this is an area worth some
> thought, which the extra-class LSP draft seems to have initiated.

I agree that it is worthy of thought and debate and that the draft has been
a very useful stimulus. The disucssion of a BCP may be premature unless some
vendors and SPs have deployment experience of this issue.  I guess before
going too much further down the path of "extra-class" I'd like to be certain
that we really don't have adequate mechanisms to handle the issues.

Cheers,
Adrian